1. Field of Invention
This invention relates to a technique for optimizing the performance of cyclones, e.g., operating in a hydrocyclone battery in a mineral extraction processing system, including extracting a mineral from ore.
2. Description of Related Art
By way of example, the aforementioned patent application Ser. No. 13/389,546 (712-2.330-1-1//CCS-0026, 43 and 44) discloses techniques for performance monitoring of individual cyclones using a SONAR-based slurry flow measurement, e.g., consistent with that disclosed in relation to FIGS. 1A-1B, 2 and 3A-3D herein.
As disclosed in the aforementioned patent application Ser. No. 13/389,546, in many industrial processes the sorting, or classification, of product by size is critical to overall process performance. A minerals processing plant, or beneficiation plant, is no exception. In the case of a copper concentrator as shown in FIG. 1A, the input to the plant is water and ore (of a particular type and size distribution) and the outputs are copper concentrate and tailings. The process consists of a grinding, classification, floatation, and thickening, as shown in FIG. 1B. The grinding and classification stage produces a fine slurry of water and ore, to which chemicals are added prior to being sent to the flotation stage. Once in the flotation stage, air is used to float the copper mineral while the gangue (tailings) is depressed. The recovered copper is cleaned and dried. The tailings are thickened and sent to the tailings pond. The classification stage is critical to the performance of two areas of the process. These areas are the grinding throughput and flotation recovery, grade and throughput.
A grinding operation may include a screens and crusher stage and a mill stage, that is typically configured mills in closed circuit with a hydrocyclone battery. A hydrocyclone is a mechanical device that will separate a slurry stream whereby the smaller particles will exit out the overflow line and the larger particles will exit out the underflow line. The overflow is sent to the flotation circuit and the underflow is sent back to the mill for further grinding. A collection of these devices is called a battery. A hydrocyclone will be sized based on the particular process requirements. The performance of the hydrocyclone is dependent on how well it is matched to the process conditions. Once the proper hydrocyclone has been chosen and installed, it must be operated within a specific range in order to maintain the proper split between the overflow and the underflow. The split is dependent on slurry feed density and volumetric flow into the device. A typical control system will use a combination of volumetric flow, feed density and pressure across the hydrocyclone to control the split. Because of the harsh environmental and process conditions all of these measurements suffer from maintenance and performance issues. This can result in reduced classification performance and reduced mill throughput. Flotation performance is highly dependent on the particle size distribution in the feed which comes from the battery overflow, thus it is dependent on the hydrocyclone classification performance. The mill throughput is highly dependent on the circulation load which comes from the battery underflow. Traditionally hydrocyclone performance has been determined by evaluating manually collected samples from the consolidated hydrocyclone battery overflow stream. This technique is time consuming; the accuracy is subject to sampling techniques; the sample is a summation of all the hydrocyclones from the battery; and has a typical 24 hour turnaround time. Therefore it is not possible to implement a real time control algorithm to monitor, control, and optimize the each individual hydrocyclone.
Real time monitoring of each individual hydrocyclone would provide the ability to track the performance of individual hydrocyclones. This would enable the following:                The detection of hydrocyclones that require maintenance or have become plugged.        The detection of operational performance instabilities that cause extended periods of roping or surging.        The detection of chronic problems with certain hydrocyclones.        Tighter classification control with changing throughput demands and feed densities.        Increased up time or availability of the hydrocyclone battery.        
Another common problem with hydrocyclone monitoring is reliably determining if a feed gate valve is open or closed. This is typically done using two micro switches. One switch indicates the valve is in the open position and the other switch indicates it is in the closed position. These switches are typically unreliable and require constant maintenance. A reliable maintenance free method is needed.
Moreover, FIG. 2 shows a classification stage generally indicated as 10 that may form part of a mineral extraction processing system, like the one shown in FIGS. 1A and 1B for extracting minerals from ore. The classification stage 10 includes a hydrocyclone battery 12 that receives a feed from a grinding stage, as shown in FIG. 1B. The hydrocyclone battery 12 is configured to respond to signaling from a signal processor or processor control module 14, and provide an effluent, e.g., a fine slurry or slurry feed, to a flotation stage shown in FIG. 1B. The classification stage 10 also may include a hydrocyclone split 16 that receives the slurry from the hydrocyclone battery 12, and also may receive signaling from the signal processor or processor control module 14, and may provide some portion of the slurry back to the mill stage shown in FIG. 1B, and may also provide another portion of the slurry as a flotation feed to a flotation stage shown in FIG. 1B consistent with that described in the aforementioned PCT application serial no. PCT/US09/43438. The signal processor or processor control module 14 may also send to or receive from one or more signals with a control room computer 50 (see FIG. 3A). The technique to track the flow performance of individual cyclones operating in parallel on a single battery is described in relation to the hydrocyclone battery 12 (i.e. the single battery), the signal processor or processor control module 14 and the cooperation of these two components.
FIG. 3A shows the hydrocyclone battery 12 (i.e. the single battery), the signal processor or processor control module 14 and the cooperation of these two components according to some embodiments of the present invention. For example, the hydrocyclone battery 12 may include a first and second hydrocyclone pair 12a, 12b. The first hydrocyclone pair 12a includes a first hydrocyclone 20 and a second hydrocyclone 30. The first hydrocyclone 20 has a cylindrical section 22 with an inlet portion 22a for receiving via a feed pipe 9 the feed from the grinding stage shown in FIG. 1B, an overflow pipe 24 for providing one portion of the fine slurry or slurry feed to either the flotation stage shown in FIG. 1B, or the hydrocyclone split 16 shown in FIG. 2, and has a conical base section 26 with underflow outlet 26a for providing a remaining portion of the fine slurry or slurry feed. See also FIG. 3B, which shows, by way of example, the cyclone 20 in enlarged detail.
Similarly, the second hydrocyclone 30 has a cylindrical section 32 with an inlet portion 32a for receiving the feed from the grinding stage shown in FIG. 1B, an overflow pipe 34 for providing one portion of the fine slurry or slurry feed to either the flotation stage shown in FIG. 1B, or the hydrocyclone split 16 shown in FIG. 2, and has a conical base section 36 with underflow outlet 36a for providing a remaining portion of the fine slurry or slurry feed.
As one skilled in the art would appreciate, the first and second hydrocyclones 20, 30 classify, separate and sort particles in the feed from the grinding stage based at least partly on a ratio of their centripetal force to fluid resistance. This ratio is high for dense and course particles, and low for light and fine particles. The inlet portion 22a, 32a receives tangentially the feed from the grinding stage shown in FIG. 1B, and the angle and the length of the conical base section 26, 36 play a role in determining its operational characteristics, as one skilled in the art would also appreciate.
At least one sensor 28 may be mounted on the overflow pipe 24 that is configured to respond to sound propagating in the overflow pipe 24 of the cyclone 20, and to provide at least one signal containing information about sound propagating through the slurry flowing in the overflow pipe 24 of the cyclone 20. Similarly, at least one corresponding sensor 38 is mounted on the overflow pipe 34 that is configured to respond to sound propagating in the overflow pipe 34 of the cyclone 30, and to provide at least one corresponding signal containing information about sound propagating through the slurry flowing in the overflow pipe 34 of the cyclone 30. By way of example, the at least one sensors 28, 38 may take the form of a SONAR-based clamp-around flow meter, which is known in the art consistent with that described below. The SONAR-based clamp-around flow meters 28, 38 may be clamped in whole or in part around some portion of the overflow pipes 24, 34. For example, the at least one sensor or meter 28, 38 may be mounted on the top of the overflow pipes 24, 34, or the at least one sensor or meter 28, 38 may be mounted on the bottom of the overflow pipe 24, 34. Alternatively, a pair of at least one sensor or meter 28, 38 may be mounted on the overflow pipes 24, 34, e.g., with one sensor or meter mounted on the top of the overflow pipes 24, 34, and with another sensor or meter mounted on the bottom of the overflow pipe 24, 34.
By way of example, in operation the SONAR-based clamp-around flow meters 28, 38 may be configured to respond to a strain imparted by the slurry, e.g., made up of water and fine particles, flowing in the overflow pipes 24, 34 of the cyclones 20, 30, and provide the signals along signal paths or lines 28a, 38a containing information about sound propagating through the slurry flowing in the overflow pipes 24, 34 of the cyclones 20, 30.
The classification stage 10 may include a signal processor or processor control module 14 (FIG. 2), which is also shown in FIG. 3A, having at least one module configured to respond to the signals along the signal paths or lines 28a, 38a containing information about sound propagating through the slurry flowing in the overflow pipes 24, 34 of cyclones 20, 30 operating in parallel on the cyclone battery 12 (see also FIG. 2), and determine the performance of individual cyclones 20, 30 based at least partly on the information contained in the signals. The signal processor or processor control module 14 may also send to or receive from one or more signals along signal path or line 14a with the control room computer 50 (see FIG. 2). The signal processor or processor control module 14 may also be configured to respond to signaling containing information about a battery flow rate, battery pressure, feed density, and cyclone status as indicated by individual gate valve positions of respective cyclones, which are provided from the cyclone battery 12 (FIG. 2).
Furthermore, in order to implement the technology set forth in the aforementioned patent application Ser. No. 13/389,546, embodiments included at least one sensor or meter 28a, 28b, 28c, 28d mounted on other parts of the cyclone or cyclone battery, or other parts or pipes connected to the cyclone or cyclone battery, including the feed pipe 9, or the inlet portion 22a, 32a, or the cylindrical section 22, 32, or the conical base section 26, 36, or the underflow outlet 26a, 36a, or some combination thereof, as shown by way of example in FIG. 3B.